The present invention relates to a transformer system and a direct current (dc) power supply constructed to obtain a direct current power, thereby supplying a stable dc power without noise irrespective of a kind of external power supply connected to the primary coil side thereof.
According to the transformation process in the conventional transformer system, when a voltage of an alternate current (ac) power, for example, a commercial power is transformed, a transformer configured with an iron core on which coils are wound is utilized. If a dc current is to be obtained by increasing or decreasing a voltage of a dc power supply, the dc power is first transformed into ac power by use of a switching operation, then the ac current is transformed by a transformer formed with an iron core on which coils are wound.
In the transform operation of this transformer, an ac power must be supplied to the primary coil thereof so that an ac power is induced on the side of a secondary coil according to a change in a magnetic flux generated by the ac current flowing through the primary coil.
In order to transform this ac power into dc power, the ac power must be subjected to a rectification.
However, when an alternating current is converted into a direct current, the resultant direct current is accompanied by an ac component which appears as a pulsating current in the direct current.
The pulsating current appearing in the direct current thus obtained by use of a transformer and a rectifier exists in any case, and it is impossible at present to completely remove the pulsating current.
A transformer system including such a transformer has such serious drawbacks that the direct current output from the secondary coil side contains the pulsating current and, since the primary coil is linked to the secondary coil by a magnetic flux in this transformer, noise on the primary coil side is transferred to the secondary coil side and appears in the power supplied from the secondary coil side.
According to the conventional complex method for eliminating the noise, a filter having a fixed bandpass is disposed to remove the noise, and thus primary power from which the noise has been removed is supplied to the transformer. However, due to the operational principle of the transformer, it is impossible to obtain from an ac power supply a dc current free from the pulsating current, switching noise, and the transferred noise by use of the transformer.
Moreover, the magnetic flux generated in a transformer has a great influence on the environments thereof, so as to cause serious trouble to electronic devices such as a computer which handles a magnetic recording medium.
To prevent such an influence, a complete magnetic isolation is necessary for the transformer. As a result, the structure of the system using this transformer becomes complicated, the shape thereof is restricted, and the installation place is limited.
The present invention relates to a transformer system and a dc power supply including the same in which the problems of the conventional apparatus are solved.